# What is refractive index?

The refractive index of a substance is a dimensionless quantity that explains how fast light passes through it in optics. Its formula is:

Here V is the wave velocity of light in the medium, and C is the speed of light in vacuum. Suppose, water has a refractive index of 1.333. Its means light pass in water 1.333 times slower than in air. When the refractive index of a substance is increased, the speed of light in that substance is decrease.

In 1807, Thomas Young is thought to have first used and created the term “index of refraction.” Simultaneously, he converted this refractive power value into a single number, rather than the conventional ratio of two integers.

When light enters a material, the refractive index influences how much the path of light is bent, or refracted. The measured values also govern how much light is reflected at the connection, as well as the critical angle for total internal reflection, intensity, and Brewster’s angle.

The refractive index can be thought of as the factor that reduces the speed and wavelength of radiation when compared to their vacuum values.

The refractive index can change depending on the wavelength. When white light is refracted, it splits into constituent hues. This is referred to as dispersion. Prisms and rainbows, as well as chromatic aberration in lenses, define this concept. A complex-valued refractive index can be used to describe light propagation in absorbing materials.

After that, the imaginary part is in charge of weakness, while the actual portion is in charge of refraction. Across the visible spectrum, the refractive index of most elements changes by many percent with wavelength.

From X-rays to radio waves, the idea of refractive index holds across the electromagnetic spectrum. It can also be used to explain wave concept like sound. The speed of sound is employed alternative of the speed of light in this situation, and a recommendation medium other than vacuum must be selected.

A lens made of a high refractive index material is smaller and thus lighter than a lens made of a lower refractive index material for lenses (such as eye glasses). The cost of producing such lenses is typically higher than that of ordinary lenses.